Fungi are known to cause a variety of infectious diseases in man, animals, and plants. In man, for instance, they cause superficial mycosis affecting the skin, oral cavity, etc. and systemic mycosis affecting the viscera, brain, etc. They cause similar infections in pet and domestic animals as well. Furthermore, fungi inflict various hazardous effects on plants such as orchard trees and vegetables.
As the principal pathogenic fungi causing systemic mycosis in man, those of the genera Candida, Cryptococcus, and Aspergillus, among others, are known. As to superficial mycosis, Candida species affecting the skin, oral cavity, and vagina and trichophytons infecting the skin of the extremities are regarded as the major pathogenic fungi. Besides those fungi, many other fungi exist in the environment and are suspected to contaminate the animal and vegetable kingdoms.